One or more embodiments relate to a nonvolatile memory device and a method of programming the device.
Recently, there is an increasing demand for nonvolatile memory devices which can be electrically programmed and erased and which do not require the refresh function of rewriting data at specific intervals.
The nonvolatile memory cell of the nonvolatile memory device can be electrically programmed and erased, and the program and erase operations are performed using the threshold voltage of the cell which varies when electrons are moved by a strong electric field applied to the thin oxide layer of the cell.
The nonvolatile memory device for the most part includes a memory cell array in which memory cells for storing data are arranged in a matrix form and page buffers for writing data into respective specific memory cells of the memory cell array or for reading data stored in respective specific memory cells. The page buffers each include a pair of bit lines coupled to specific memory cells, a register configured to temporarily store data to be written into specific memory cells or to temporarily store data read from specific memory cells, a sense node configured to sense the voltage level of a specific bit line or a specific register, and a bit line selection unit configured to control whether or not to couple the specific bit line to the sensing node.
In such a program operation of the nonvolatile memory device, a bouncing phenomenon is generated in which a voltage level of the common source line is changed according to the program state of peri (peripheral) cells, which causes the level of current flowing through a specific memory cell to vary. Accordingly, an under-programmed cell is recognized as having been programmed even though the cell has not been programmed.